Reclaiming device, method, and recovery unit of CO2, H2S, or both of CO2 and H2S

ABSTRACT

Provided are a reclaimer  51  that introduces, through a branch line L 11 , and stores a part  17   a  of an absorbent  17  regenerated in a regenerator of a recovery unit that recovers CO 2  or H 2 S in a gas, a first alkaline agent supply section  53 A that supplies an alkaline agent  52  to the reclaimer  51 , a heating section  54  that heats the absorbent  17  stored in the reclaimer  51  and to which the alkaline agent  52  has been mixed to obtain recovered vapor  61 , a first vapor cooler  55 A that cools the recovered vapor  61  discharged from the reclaimer  51  through a vapor line L 12 , a first gas-liquid separator  56 A that separates a coexisting substance  62  entrained in the cooled recovered vapor  61  into a recovered absorption agent vapor (gas)  17   b  and the liquid coexisting substance  62  by gas-liquid separation, and an introduction line L 13  that introduces the recovered absorption agent vapor  17   b  separated in the first gas-liquid separator  56 A into a regenerator  20.

FIELD

The present invention relates to a reclaiming device, a method, and arecovery unit of CO₂, H₂S, or both of CO₂ and H₂S.

BACKGROUND

In recent years, as a cause of global warming of the earth, thegreenhouse effect due to CO₂ has been pointed out, and measures againstthe greenhouse effect is internationally imperative in terms ofprotection of the earth environment. Generation sources of CO₂ extendover every field of human activities that burn fossil fuels, and demandsfor suppression of emission of CO₂ tends to increase. In response to thedemands, a method of bringing a flue gas in a boiler in contact with anamine-based CO₂ absorbent such as an alkanolamine aqueous solution, andremoving and recovering CO₂ in the flue gas, and a method of storing therecovered CO₂ without emitting CO₂ to the air have been vigorouslystudied for power generation facilities such as thermal power stationsthat use a large amount of fossil fuels.

Conventionally, Patent Literature 1 discloses a method of removing CO₂(carbon dioxide) and SOx (sulfur oxide) in a flue gas. This methodincludes a denitrification process of reducing NOx (nitrogen oxide)contained in a flue gas to perform denitrification treatment, adesulfurization process of bringing SOx contained in the flue gas incontact with calcium carbonate in slurry to perform desulfurizationtreatment, and a CO₂ desorption process of bringing the flue gassubjected to the denitrification treatment and the desulfurizationtreatment in countercurrent contact with an amine-based absorbent(alkanolamine aqueous solution) in an absorber to cause the absorbent toabsorb CO₂ in the flue gas, and an absorbent regenerating process ofobtaining a lean solution by removing CO₂ from a rich solution that hasabsorbed CO₂ in a regenerator and returning the lean solution to theabsorber again. Then, in this method, to prevent a situation where athermally stable salt resulted from oxidative degradation ofalkanolamine by oxygen in the flue gas or a reaction of alkanolaminewith residual NOx or residual SOx, and a solid such as dust contained inthe flue gas are accumulated in a system that the absorbent, passesthrough, reclaiming is performed, which includes heating the absorbentin a reclaimer, concentrating a coexisting substance as sludge, andremoving the deteriorated substance from the absorbent.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Laid-open Patent Publication No. 5-245339

SUMMARY Technical Problem

However, in a conventional reclaiming operation, while ionic substancesand solid substances having no vapor pressure, and high-boiling pointsubstances are separated and removed as reclaimer residues, low-boilingpoint substances and substances having a vapor pressure similarly toabsorption agents are entrained in recovered vapor recovered from thereclaimer. Therefore, there is a problem that separation/removal ofabsorbent coexisting component is insufficient.

Therefore, a reclaiming device that prevents the introduction of anabsorbent coexisting component together with recovered vapor recoveredfrom a reclaimer to a regenerator, when regenerating an absorbent in thereclaimer, has been de sired.

In view of the foregoing, an objective of the present invention is toprovide a reclaiming device, a method, and a recovery unit of CO₂, H₂S,or both of them, which can prevent entrainment of a fluid in a reclaimerwith recovered vapor recovered from a reclaimer, and the introduction ofan absorbent, coexisting component together with the recovered vapor tothe regenerator.

Solution to Problem

The first aspect of the present invention in order to solve the abovementioned problem is a reclaiming device including a reclaimerconfigured to introduce and store a part of an absorbent regenerated ina regenerator of a recovery unit that recovers CO₂ or H₂S in a gas, afirst alkaline agent supply section configured to supply an alkalineagent, to the reclaimer, a heating section configured to heat theabsorbent stored in the reclaimer and to which the alkaline agent hasbeen mixed to obtain recovered vapor, a vapor cooler configured to coolthe recovered vapor discharged from the reclaimer through a vapor line,a first gas-liquid separator configured to separate a coexistingsubstance entrained in the cooled recovered vapor into recoveredabsorption agent vapor and a liquid coexisting substance by gas-liquidseparation, and an introduction line configured to introduce therecovered absorption agent vapor separated in the first gas-liquidseparator to the regenerator.

The second aspect of the invention is the reclaiming device according tothe first aspect, wherein the first vapor cooler includes a first coolerconfigured to perform cooling with reflux water from the regenerator,and a second cooler provided at a downstream side of a rich/leansolution heat exchanger disposed in a lean solution supply line, andconfigured to cool the recovered vapor with a rich solution.

The third aspect of the invention is a reclaiming device including areclaimer configured to introduce and store a part of an absorbentregenerated in an regenerator of a recovery unit that recovers CO₂ orH₂S in a gas, a first alkaline agent supply section configured to supplyan alkaline agent, to the reclaimer, a heating section configured toheat the absorbent stored in the reclaimer and to which the alkalineagent has been mixed to obtain recovered vapor, a second vapor coolerconfigured to cool the recovered vapor discharged from the reclaimerthrough a vapor line, a first gas-liquid separator configured toseparate a coexisting substance entrained in the cooled recovered vaporinto recovered absorption agent vapor and a liquid coexisting substanceby gas-liquid separation, a cooler configured to cool the separatedrecovered absorption agent vapor, a second gas-liquid separatorconfigured to separate the recovered absorption agent vapor aftercooling into a low-boiling point substance flue gas and a recoveredabsorbent by gas-liquid separation, a heat, exchanger configured toperform heat exchange of the liquid coexisting substance separated inthe first gas-liquid separator with vapor condensed water from vaporsupplied to the reclaimer to increase a temperature, a CO₂ absorberconfigured to bring the liquid coexisting substance after increase inthe temperature and a CO₂ gas in contact, a second alkaline agent supplysection configured to supply the alkaline agent to the liquid coexistingsubstance after absorption of CO₂, and a distiller configured to distillthe liquid coexisting substance to which the alkaline agent has beensupplied while introducing the CO₂ thereinto.

The fourth aspect of the invention is the reclaiming device according tothe third aspect, wherein the second vapor cooler includes a firstcooler configured to perform cooling with the liquid coexistingsubstance separated from the recovered vapor in the first gas-liquidseparator by gas-liquid separation, a second cooler configured toperform cooling with reflux water from the regenerator, and a thirdcooler provided at a downstream side of a rich/lean solution heatexchanger disposed in a lean solution supply line, and configured tocool, with a rich solution, the recovered vapor after cooling with thesecond cooler.

The fifth aspect of the invention is the reclaiming device according tothe third or fourth aspect, including a CO₂ gas introduction lineconfigured to introduce the CO₂ discharged from the CO₂ absorber intothe distiller, and a nitrogen supply section configured to introduce anitrogen gas into the CO₂ gas introduction line.

The sixth aspect of the invention is a reclaiming method including, whenrecovering, in a reclaimer, a part of circulating absorbent thatrecovers CO₂ or H₂S in a flue gas in a CO₂ or H₂S recovery unit asrecovered vapor, cooling the recovered vapor from the reclaimer, andthen separating an entrained coexisting substance by gas-liquidseparation to remove a liquid coexisting substance, and introducingrecovered absorption agent vapor after the gas-liquid separation into anabsorbent regenerator.

The seventh aspect of the invention is the reclaiming method accordingto the sixth aspect, including cooling the recovered absorption agentvapor to obtain a liquid recovered absorbent in the introducing therecovered absorption agent vapor after separation into the absorbentregenerator, heating the separated liquid coexisting substance, thenbringing the liquid coexisting substance and a CO₂ gas in contact, andthen supplying an alkaline agent, and distilling, in a distiller, theliquid coexisting substance into which the alkaline agent has beensupplied while introducing the CO₂ thereto.

The eighth aspect of the invention is the reclaiming method according tothe seventh aspect, wherein a nitrogen gas is added to the CO₂ gas to beintroduced into the distiller.

The ninth aspect of the invention is a recovery unit of CO₂, H₂S, orboth of CO₂ and H₂S, including an absorber configured to bring a gascontaining CO₂, H₂S, or both of CO₂ and H₂S and an absorbent in contactto remove CO₂, H₂S, or both of CO₂ and H₂S, an absorbent regeneratorconfigured to regenerate a solution that has absorbed CO₂, H₂S, or bothof CO₂ and H₂S to obtain the absorbent, and the reclaiming deviceaccording to any one of the first to the fifth aspects, configured toextract a part of the absorbent regenerated in the regenerator, and toremove a coexisting substance in the absorbent, wherein the absorbentregenerated in the absorbent regenerator is circulated and reused in theabsorber, and recovered vapor recovered from the reclaiming device isintroduced into the regenerator.

Advantageous Effects of Invention

According to the present invention, by performing selectiveseparation/removal of an absorbent coexisting component entrained inrecovered vapor from a reclaimer, improvement of operation reliabilityincluding reduction of absorbent corrosiveness can be achieved. Further,improvement of absorption agent recovery performance can be achieved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of a CO₂ recovery unit according to afirst embodiment.

FIG. 2 is a schematic diagram of a reclaiming device according to thefirst embodiment.

FIG. 3 is a schematic diagram of another reclaiming device according tothe first embodiment.

FIG. 4 is a schematic diagram of a reclaiming device according to asecond embodiment.

FIG. 5 is a schematic diagram of another reclaiming device according tothe second embodiment.

FIG. 6 is a schematic diagram of a reclaiming device according to athird embodiment.

FIG. 7 is a diagram illustrating selective removal ratios in recoveredvapor in a conventional example and the first embodiment.

FIG. 8 is a diagram illustrating selective removal ratios in recoveredvapor in a conventional example and the second embodiment.

FIG. 9 is a diagram illustrating recovery ratios of an absorption agentin the first embodiment and the second embodiment.

FIG. 10 is a diagram illustrating selective removal ratios in recoveredvapor in a conventional example and the third embodiment.

FIG. 11 is a diagram illustrating recovery ratios of an absorption agentin the first embodiment and the third embodiment.

DESCRIPTION OF EMBODIMENTS

Hereinafter, favorable embodiments of the present invention will bedescribed in detail with reference to the appended drawings. Note thatthe present invention is not limited by the embodiments, and when thereis a plurality of embodiments, the present invention includes thoseobtained by combining the embodiments.

First Embodiment

While an employable process to remove CO₂, H₂S, or both of them in a gasof the present invention is not especially limited, an example of aremoving device that removes CO₂ will be described with reference toFIG. 1.

Examples of gases to be treated by the present invention include a coalgasifier gas, a synthesis gas, a coke oven gas, a petroleum gas, anatural gas, and a combustion flue gas. However, the gases are notlimited to these examples, and any gas can be employed as long as thegas contains an acid gas such as CO₂ or H₂S.

In the following embodiment, a flue gas containing CO₂ as the acid gaswill be described.

FIG. 1 is a schematic diagram illustrating a configuration of a CO₂recovery unit according to the first embodiment. As illustrated in FIG.1, a CO₂ recovery unit 12 according to the first embodiment includes aflue gas cooling device 16 that cools a flue gas 14 containing CO₂ andCO₂ discharged from an industrial combustion facility 13 such as aboiler or a gas turbine with cooling water 15, a CO₂ absorber(hereinafter, also referred to as “absorber”) 18 including a CO₂recovery section 18A that brings the cooled flue gas 14 containing CO₂and a CO₂ absorbent (hereinafter, also referred to as “absorbent”) 17that absorbs CO₂ in contact to remove CO₂ from the flue gas 14, and anabsorbent regenerator (hereinafter, also referred to as “regenerator”)20 that desorbs CO₂ from a CO₂ absorbent (hereinafter, also referred toas “rich solution”) 19 that has absorbed CO₂ to regenerate a CO₂absorbent. Then, in the CO₂ recovery unit 12, the regenerated CO₂absorbent (hereinafter, also referred to as “lean solution”) 17 fromwhich CO₂ has been removed in the absorbent regenerator 20 is reused inthe CO₂ absorber 18 as the CO₂ absorbent.

Note that, in FIG. 1, the reference sign 13 a is a flue gas duct, 13 bis a stack, 27 a is steam condensed water. There are two cases for theCO₂ recovery unit 12, which includes a case of providing the CO₂recovery unit later to recover CO₂ from an already provided flue gassource, and a case of placing the CO₂ recovery unit along with a newlyprovided flue gas source at the same time. An openable/closable damperis installed to the stack 13 b, and is closed at the time of anoperation of the CO₂ recovery unit 12. Further, the damper is set toopen when the operation of the CO₂ recovery unit 12 is stopped althoughthe flue gas source is operated.

In a method of recovering CO₂ using the CO₂ recovery unit 12, first, apressure of the flue gas 14 containing CO₂ from the industrialcombustion facility 13 such as a boiler or a gas turbine is increased bya flue gas blower 22, and the flue gas 14 is then sent to the flue gascooling device 16, cooled with the cooling water 15, and sent to the CO₂absorber 18.

In the CO₂ absorber 18, the flue gas 14 is brought in countercurrentcontact with the CO₂ absorbent 17 that is an amine absorbent accordingto the present embodiment, and CO₂ in the flue gas 14 is absorbed in theCO₂ absorbent 17 by a chemical reaction.

The CO₂-removed flue gas from which CO₂ has been removed in the CO₂recovery section 18A is brought, in gas-liquid contact with circulatingrinse water 21 containing the CO₂ absorbent supplied through a nozzle ina water cleaning section 18B of the CO₂ absorber 18, the CO₂ absorbent17 entrained in the CO₂-removed flue gas is recovered, and then a fluegas 23 from which CO₂ has been removed is discharged outside the system.

Further, a pressure of the rich solution that is the CO₂-absorbed CO₂absorbent 19 is increased by a rich solution pump 24, heated with thelean solution that, is the CO₂ absorbent 17 regenerated in the absorbentregenerator 20, in a rich/lean solution heat exchanger 25 disposed on arich solution supply line L₁, and supplied to the absorbent regenerator20.

The rich solution 19 discharged from an upper portion to an inside ofthe absorbent regenerator 20 causes an endothermic reaction by watervapor supplied from a bottom portion, and desorbs most of CO₂. The CO₂absorbent that has desorbed a part or most of CO₂ in the absorbentregenerator 20 is called semi-lean solution. This semi-lean solutionbecomes the CO₂ absorbent (lean solution) 17 from which nearly all ofCO₂ has been removed, when the semi-lean solution is about to reach thebottom portion of the absorbent regenerator 20. A part of the leansolution 17 is heated with water vapor 27 in a regenerating heater 26,and supplies water vapor to the inside of the absorbent regenerator 20.

Meanwhile, a CO₂-entrained gas 28 accompanied by the water vapordischarged from the rich solution 19 and the semi-lean solution in theregenerator is led from a top of the absorbent regenerator 20, the watervapor is condensed by a condenser 29, water is separated in a separationdrum 30, and a CO₂ gas 40 is discharged outside the system and isseparately compressed by a compressor 41 and recovered. Thiscompressed/recovered CO₂ gas 42 is pressed into an oil field using anenhanced oil recovery method (EOR) or stored in an aquifer after througha separation drum 43 to achieve measurements against the global warming.

Reflux water 31 separated/refluxed from the CO₂-entrained gas 28accompanied by the water vapor in the separation drum 30 is supplied tothe upper portion of the absorbent regenerator 20 and the rinse water 21side with a reflux water circulation pump 35.

The regenerated CO₂ absorbent (lean solution) 17 is cooled with the richsolution 19 in the rich/lean solution heat exchanger 25 disposed on anintersection of the rich solution supply line L₁ and a lean solutionsupply line L₂, then a pressure is increased by a lean solution pump 32,and the CO₂ absorbent (lean solution) 17 is cooled in a lean solutioncooler 33 and is then supplied to the CO₂ absorber 18. Note that, inthis embodiment, an outline has been merely described. Description isgiven omitting a part of devices that come with the CO₂ recovery unit.

A part of the CO₂ absorbent 17 regenerated in the absorbent regenerator20 is branched at a branch line L₁₁ from the lean solution supply lineL₂ and introduced into a reclaimer 51, and the water vapor 27 issupplied to indirectly heat the absorbent, so that a coexistingsubstance is separated.

FIG. 2 is a schematic diagram of a reclaiming device according to thefirst embodiment.

As illustrated in FIG. 2, a reclaiming device according to the presentembodiment includes the reclaimer 51 that introduces, through a branchline L₁₁, and stores a part 17 a of the absorbent 17 regenerated in theregenerator of the recovery unit that recovers CO₂ or H₂S in a gas, afirst alkaline agent supply section 53A that supplies an alkaline agent52 to the reclaimer 51, a heating section 54 that heats the absorbent 17stored in the reclaimer 51 and to which the alkaline agent 52 has beenmixed to obtain recovered vapor 61, a first vapor cooler 55A that coolsthe recovered vapor 61 discharged from the reclaimer 51 through a vaporline L₁₂, a first gas-liquid separator 56A that separates a coexistingsubstance 62 entrained in the cooled recovered vapor 61 into recoveredabsorption agent vapor (gas) 17 b and a liquid coexisting substance 62by gas-liquid separation, and an introduction line L₁₃ that introducesthe recovered absorption agent vapor 17 b separated in the firstgas-liquid separator 56A into the regenerator 20.

Note that, the reference sign 57 in the drawing illustrates a coexistingsubstance cooler that cools the coexisting substance (liquid) 62 afterthe gas-liquid separation, and the reference sign 58 illustrates areclaimer residue.

The temperature of the recovered vapor 61 discharged from the reclaimer51 is decreased by the first vapor cooler 55A by about 6 to 7° C.

In the reclaimer 51, the coexisting substance 62 having a vapor pressureis entrained in the recovered vapor 61. Therefore, the entrainedcoexisting substance 62 can be separated and removed by performingseparation using the first gas-liquid separator 56A as in the presentembodiment.

That, is, the coexisting substance 62 having a higher boiling point thanamines in a free state of the absorbent is cooled in the first vaporcooler 55A, and the temperature is decreased by about 6 to 7° C., sothat the coexisting substance 62 is liquefied and separated in the firstgas-liquid separator 56A. When a temperature (T₁) of the recovered vapor61 is 130° C., the recovered vapor 61 is cooled in the first vaporcooler 55A, and a temperature (T₂) of the recovered vapor 61 aftercooling is made to 123° C., so that the coexisting substance (liquid) 62can be separated.

An effect of the present embodiment will be described with reference toFIG. 7.

FIG. 7 is a diagram illustrating selective removal ratios in recoveredvapor in a conventional example and the first embodiment (where theconventional example is a reference (1)). The conventional technology isa case of recovering the recovered vapor 61 from the reclaimer 51 as itis without providing the gas-liquid separator as in the presentembodiment.

The selection removal ratio of the coexisting substance 62 from therecovered vapor 61 in the present embodiment is 40, and the coexistingsubstance can be substantially removed, where the conventional exampleis the reference (1).

Further, in the present embodiment, as illustrated in FIG. 3, a firstcooler 55A-1 that performs cooling using the reflux water 31 from theregenerator 20 of the CO₂ recovery unit 12, and a second cooler 55A-2provided at a downstream side of a rich/lean solution heat exchanger 25disposed at an intersection of the rich solution supply line L₁ and thelean solution supply line L₂, and which cools the recovered vapor 61with the rich solution 19 are included as the first vapor cooler 55A.

Accordingly, when the temperature (T₁) of the recovered vapor 61 is 130°C., the recovered vapor is cooled to the temperature (T₂=125° C.) by thefirst cooler 55A-1, and then cooled to a temperature (T₃=123° C.) by thesecond cooler 55A-2.

Here, the reflux water 31 is brought to pass through a coexistingsubstance cooler 57 for cooling the coexisting substance (liquid) 62separated in the first gas-liquid separator 56A, and is then introducedinto the first cooler 55A-1 through a cooling water line L₁₄.

The first cooler 55A-1 is provided at an intersection of the vapor lineL₁₂ and the cooling water line L₁₄ and the second cooler 55A-2 isprovided at an intersection of the vapor line L₁₂ and the rich solutionsupply line L₁, and thus cooling is possible with heat in the system ofthe CO₂ recovery unit 12.

Second Embodiment

A reclaiming device according to an embodiment of the present inventionwill be described with reference to the drawings. FIG. 4 is a schematicdiagram of a reclaiming device according to a second embodiment. FIG. 5is a schematic diagram of another reclaiming device according to thesecond embodiment. Note that the same member as the first embodiment isdenoted with the same reference sign, and description thereof isomitted.

As illustrated in FIG. 4, a reclaiming device according to the presentembodiment includes a reclaimer 51 that introduces, through a branchline L₁₁, and stores a part 17 a of an absorbent 17 regenerated in aregenerator of a recovery unit that recovers CO₂ or H₂S in a gas, afirst alkaline agent supply section 53A that supplies an alkaline agent52 to the reclaimer 51, a heating section 54 that heats the absorbent 17stored in the reclaimer 51 and to which the alkaline agent 52 has beenmixed to obtain recovered vapor 61, a second vapor cooler 55B that coolsrecovered vapor 61 discharged from the reclaimer 51 through a vapor lineL₁₂, a first gas-liquid separator 56A that separates a coexistingsubstance 62 entrained in the cooled recovered vapor 61 into recoveredabsorption agent vapor (gas) 17 b and a liquid coexisting substance 62by gas-liquid separation, a fourth cooler 71 that cools the separatedrecovered absorption agent vapor 17 b, a second gas-liquid separator 56Bthat separates the recovered absorption agent vapor 17 b after coolinginto a low-boiling point substance flue gas 72 and a recovered absorbent17 c by gas-liquid separation, a heat exchanger 63 that performs heatexchange of the liquid coexisting substance 62 separated in the firstgas-liquid separator 56A with vapor condensed water 27 a from vapor 27supplied to the reclaimer 51 to increase the temperature, a CO₂ absorber64 that brings the liquid coexisting substance 62 after increase in thetemperature, and a CO₂ gas (recovered CO₂) 40 in contact, a secondalkaline agent supply section 53B that supplies an alkaline agent 52 toa liquid coexisting substance 62A after absorption of CO₂, and adistiller 68 that distills a liquid coexisting substance 62B to whichthe alkaline agent 52 has been supplied while introducing the CO₂ gas(recovered CO₂) 40 thereto. Further, a coexisting substance (liquid) 63Ais discharged from the distiller 68. Further, CO₂ discharged from theCO₂ absorber 64 is introduced into the distiller 68 through a CO₂ gasintroduction line L₂₁.

In the present embodiment, the recovered vapor 61 is cooled in thesecond vapor cooler 55B, and then separated into recovered absorptionagent vapor (gas) 17 b and the liquid coexisting substance 62 bygas-liquid separation in the first gas-liquid separator 56A.

A volatile low-boiling point substance such as ammonia is entrained inthis recovered adsorbent vapor (gas) 17 b. Therefore, the recoveredadsorbent vapor (gas) 17 is cooled in a fourth cooler 71 and isintroduced into the second gas-liquid separator 56B, and the low-boilingpoint substance flue gas 72 is separated. This separated low-boilingpoint substance flue gas 72 is introduced into a top of the absorber 18.Reflux water 31 from a CO₂ recovery unit 12 is introduced into thefourth cooler 71 to perform cooling.

Further, the temperature of the separated liquid coexisting substance 62is increased in the heat exchanger 63 by subjecting to heat exchangewith the vapor condensed water 27 a from the vapor 27 supplied to thereclaimer 51, and the liquid coexisting substance 62 after increase inthe temperature is introduced into the CO₂ absorber 64 into which a CO₂gas 40 is introduced. In the CO₂ absorber 64, the liquid coexistingsubstance 62 is brought into countercurrent contact, with the recoveredCO₂ gas 40 to react with CO₂. As the CO₂ gas 40, the CO₂ gas 40recovered in the CO₂ recovery unit 12 is used.

Following that, amines of the absorption agent are made into amines in afree state by supplying the alkaline agent 52 from the second alkalineagent supply section 53B to the liquid coexisting substance 62A, andmaking a pH of the liquid coexisting substance 62A high (for example, byabout 0.3 to 0.5).

Following that, the liquid coexisting substance 62B to which thealkaline agent 52 has been added is introduced into the distiller 68,and in performing distillation here, the coexisting substance 62Babsorbs the introduced CO₂ gas 40 and is on a liquid side. Therefore,the coexisting substance 62B loses a vapor pressure.

The absorption agent is in a vapor state with a high pH by release of arelease valve 67. Therefore, the absorption agent, does not react withthe CO₂ gas 40 and is separated as vapor by the distillation in thedistiller 68.

Here, the CO₂ gas 40 introduced into the distiller 68 is CO₂ dischargedfrom the CO₂ absorber 64 and introduced through the CO₂ gas introductionline L₂₁.

The coexisting substance (liquid) 63A separated in the distiller 68 iscooled in a coexisting substance cooler 57. Note that, as a refrigerantused in the coexisting substance cooler 57, the reflux water 31 from theCO₂ recovery unit 12 is introduced to perform cooling in the presentembodiment. Then, the cooled reflux water 31 is introduced into thefourth cooler 71 through a cooling water line L₁₄, and then introducedinto the reclaimer 51.

An effect of the present embodiment will be described with reference toFIG. 8.

FIG. 8 is a diagram illustrating selective removal ratios in recoveredvapor in a conventional example and the second embodiment (where theconventional example is a reference (1)). The conventional technology isa case of recovering the recovered vapor 61 from the reclaimer 51 as itis without providing the first gas-liquid separator 56A and the secondgas-liquid separator 56B as in the present embodiment.

The selection removal ratio of the coexisting substance 62 from therecovered vapor 61 in the present embodiment is 30, and the coexistingsubstance can be substantially removed, where the conventional exampleis the reference (1).

FIG. 9 is a diagram illustrating recovery ratios of the absorption agentin the first embodiment and the second embodiment (where the firstembodiment is a reference (1)).

In a case of providing the first gas-liquid separator 56A, the secondgas-liquid separator 56B, the CO₂ absorber 64, and the distiller 68 asin the second embodiment, the recovery of the absorption agent from therecovered vapor 61 is improved by about 1.3 times.

Next, another reclaiming device according to the second embodiment willbe described.

FIG. 5 is a schematic diagram of another reclaiming device according tothe second embodiment.

In the present embodiment, as illustrated in FIG. 5, a first cooler55B-1 that performs cooling with the coexisting substance 62 separatedfrom the recovered vapor 61 in the first gas-liquid separator 56A, asecond cooler 55B-2 that performs cooling using the reflux water 31 froma regenerator 20 of the CO₂ recovery unit 12, and a third cooler 55B-3provided at a downstream side of a rich/lean solution heat exchanger 25disposed in a lean solution supply line L₁, and which cools therecovered vapor 61 with a rich solution 19 are included as the secondvapor cooler 55B.

Accordingly, when a temperature (T₁) of the recovered vapor 61 is 130°C., the recovered vapor is cooled to a temperature (T₂=128° C.) by thefirst cooler 55B-1, then cooled to a temperature (T₃=125° C.) by thesecond cooler 55B-2, and then cooled to a temperature (T₄=123° C.) bythe third cooler 55B-3.

Here, after the reflux water 31 performs cooling in the fourth cooler 71for cooling that cools the recovered absorption agent vapor (gas) 17 bseparated in the first gas-liquid separator 56A, the reflux water 31 isintroduced into the second cooler 55B-2 through the cooling water lineL₁₄, and further performs cooling.

Note that the first cooler 55B-1 is provided at an intersection of thevapor line L₁₂ and a liquid coexisting substance discharge line L₁₆, thesecond cooler 55B-2 is provided at an intersection of the vapor line L₁₂and the cooling water line L₁₄, and the third cooler 55B-3 is providedat an intersection of the vapor line L₁₂ and a rich solution line L₁,and thus cooling is possible with heat in the system of the CO₂ recoveryunit 12.

Third Embodiment

A reclaiming device according to an embodiment of the present inventionwill be described with reference to the drawing. FIG. 6 is a schematicdiagram of a reclaiming device according to a third embodiment. Notethat the same member as the first and second embodiments is denoted withthe same reference sign, and description thereof is omitted.

As illustrated in FIG. 6, the reclaiming device according to the presentembodiment further includes a CO₂ gas introduction line L₂₁ throughwhich a CO₂ gas 40 discharged from a CO₂ absorber 64 is introduced intoa distiller 68, and a nitrogen supply section 69 that introduces anitrogen (N₂) gas into the CO₂ gas introduction line L₂₁, in thereclaiming device of the second embodiment.

Since the N₂ gas is added to the CO₂ gas 40 from the nitrogen supplysection 69, a CO₂ partial pressure in the distiller 68 can be decreased.In this case, since N₂ is mixed in a recovered absorption agent (gasbody), it is desirable to supply the N₂ gas to a bottom of an absorber18 in a case of recovering CO₂ as a product. When there is no problemwith the purity of the CO₂ product, the CO₂ may be put back to aregenerator 20, as illustrated in FIG. 6.

An effect of the present embodiment will be described with reference toFIG. 10.

FIG. 10 is a diagram illustrating selective removal ratios in recoveredvapor in a conventional example and the third embodiment (where theconventional example is a reference (1)). The conventional technology isa case of recovering the recovered vapor 61 from a reclaimer 51 as it iswithout providing a first gas-liquid separator 56A, a second gas-liquidseparator 56B, a CO₂ absorber 64, and the distiller 68 as in the presentembodiment.

The selection removal ratio of a coexisting substance 62 from recoveredvapor 61 in the present embodiment is 35, and the coexisting substancecan be substantially removed, where the conventional example is thereference (1).

FIG. 11 is a diagram illustrating recovery ratios of the absorptionagent in the first embodiment and the third embodiment (where the firstembodiment is the reference (1)).

By introduction of nitrogen as in the third embodiment, the CO₂ partialpressure is decreased, addition of an alkaline agent 52 can bedecreased, and the recovery ratio of the absorption agent from therecovered vapor 61 is improved by about 1.3 times.

REFERENCE SIGNS LIST

-   -   12 CO₂ recovery unit    -   13 Industrial combustion facility    -   14 Flue gas    -   16 Flue gas cooling device    -   17 CO₂ absorbent (lean solution)    -   18 CO₂ absorber    -   19 CO₂-absorbed CO₂ absorbent (rich solution)    -   20 Absorbent regenerator    -   21 Rinse water    -   51 Reclaimer    -   52 Alkaline agent    -   55A First vapor cooler    -   55B Second vapor cooler    -   56A First gas-liquid separator    -   56B Second gas-liquid separator    -   61 Recovered vapor    -   62 Coexisting substance

The invention claimed is:
 1. A reclaiming device comprising: a reclaimerconfigured to introduce and store a part of an absorbent regenerated inan absorbent regenerator of a recovery unit that recovers CO₂ or H₂S ina gas; a first alkaline agent supply section configured to supply analkaline agent to the reclaimer; a heating section configured to heatthe absorbent stored in the reclaimer and to which the alkaline agenthas been mixed to obtain recovered vapor; a second vapor coolerconfigured to cool the recovered vapor discharged from the reclaimerthrough a vapor line; a first gas-liquid separator configured toseparate a coexisting substance entrained in the cooled recovered vaporinto recovered absorption agent vapor and a liquid coexisting substanceby gas-liquid separation; a cooler configured to cool the separatedrecovered absorption agent vapor; a second gas-liquid separatorconfigured to separate the recovered absorption agent vapor aftercooling into a low-boiling point substance flue gas and a recoveredabsorbent by gas-liquid separation; a heat exchanger configured toperform heat exchange of the liquid coexisting substance separated inthe first gas-liquid separator with vapor condensed water from vaporsupplied to the reclaimer to increase a temperature; a CO₂ absorberconfigured to bring the liquid coexisting substance after increase inthe temperature and a CO₂ gas in contact; a second alkaline agent supplysection configured to supply the alkaline agent to the liquid coexistingsubstance after absorption of CO₂; and a distiller configured to distillthe liquid coexisting substance to which the alkaline agent has beensupplied while introducing the CO₂ gas thereinto.
 2. The reclaimingdevice according to claim 1, wherein the second vapor cooler includes afirst cooler configured to perform cooling with the liquid coexistingsubstance separated from the recovered vapor in the first gas-liquidseparator by gas-liquid separation, a second cooler configured toperform cooling with reflux water from the absorbent regenerator, and athird cooler provided at a downstream side of a rich/lean solution heatexchanger disposed in a lean solution supply line, and configured tocool, with a rich solution, the recovered vapor after cooling with thesecond cooler.
 3. The reclaiming device according to claim 1,comprising: a CO₂ gas introduction line configured to introduce the CO₂gas discharged from the CO₂ absorber into the distiller; and a nitrogensupply section configured to introduce a nitrogen gas into the CO₂ gasintroduction line.